Radial-flow heat exchanger

ABSTRACT

A radial-flow heat exchanger where tubes through which one heatexchanging fluid flows surround a given axis while a second heatexchanging fluid flows across the exterior of these tubes radially with respect to the latter axis. Fluid-guides are provided for this other fluid so as to achieve at the exterior of the tubes a substantially uniform through-flow in all axial sections of the heat exchanger. The fluid-guides may include inner and outer tubular walls which taper in the same direction and define with inner and outer regions of the tubes receiving and discharge chambers for the fluid which flows radially, the receiving chamber having an inlet which forms the largest cross section of the receiving chamber while the discharge chamber has an outlet which forms the largest cross section for the discharge chamber.

finite States Patent Gilli et al. Jan. 23, 1973 [5 1 RADIAL-FLOW HEAT EXCHANGER 552,031 6/1932 Germany ..165/l22 [75] Inventors: Paul Viktor Gilli, Vienna; Kurt Fritz, Klosterneuburg; Josef M. Lip- Examiner-Mum Kaufman pitsch Graz, all of Austria. Gunther Assistant Examiner-Theophrl W. Streule Lurf, Stuttgart, Germany Attorney-Steinberg & Blake [73] Assignee: W aagner-Bir Aktiengesellschaft, [57] ABSTRACT Vienna, Austria A radial-flow heat exchanger where tubes through [22] Ffled: Sept 1970 which one heat-exchanging fluid flows surround a [21] App]. No.: 74,357 given axis while a second heat-exchanging fluid flows across the exterior of these tubes radially with respect to the latter axis. Fluid-guides are provided for this [30] Forelgn Application pnonty Data other fluid so as to achieve at the exterior of the tubes Sept. 26, 1969 Austria ..A 9159/69 a substantially uniform through-flow in all axial sections of the heat exchanger. The fluid-guides may in- [52] US. Cl ..165/l25, 261/.0ll elude inner and outer tubular walls which taper in the [5 u ..F24h same direction and define inner and outer regions [58] Field Search "165/111, 113, of the tubes receiving and discharge chambers for the 165/161463, 122-5; 62/426; 261/01 fluid which flows radially, the receiving chamber having an inlet which forms the largest cross section of [56] References C'ted the receiving chamber while the discharge chamber FOREIGN PATENTS OR APPLICATIONS has an outlet which forms the largest cross section for the discharge chamber. 974,339 12/1960 Germany ..l65/l22 858,467 1/1961 Great Britain ..26l/.0ll 17 Claims, 4 Drawing Figures I3 9 5 f at 0 z 1 I HT l8 Til 4 1 l l 1 O i O l 8 006-5 'O i 1 O O t i0 1 00880880 15 O R 88 88 O 108 00 i [6 800 g [5 008 08 00 0 1 l 8 8 3 8 2 0 r8 0 8 o P o 9 O M O l i i PATENTEUJAHN W 3,712,370

sum 2' OF 2 l0 PIC-3.2

RADIAL-FLOW HEAT EXCHANGER BACKGROUND OF THE INVENTION axis and through which the other of the pair of heat- 0 exchanging fluids flows.

Radial-flow heat exchangers are already known. However, with the conventional heat exchangers of this type there is a considerable problem encountered in connection with maintaining a uniformity of flow of the fluid at the exterior of the tubes. This latter fluid is required to flow first toward the tubes, then into heatexchanging relationship therewith, and then away from these tubes. At the present time, conventional heat exchangers of this type do not satisfactorily solve the problem of maintaining a uniformity of through-flow for the exterior fluid, so that as a result the conventional heat exchangers are not uniformly loaded. They have localized areas which are extremely hot or extremely cold, and this unavoidable lack of uniformity in the through-flow of the fluid at the exterior of the tubes in conventional radial flow heat exchangers gives rise to many serious problems resulting not only from a lack of efficiency in the operation but also from frequent failures which result in unavoidable shutting down of the heat exchanger until repairs can be carried out.

Thus, a further problem encountered with the conventional heat exchangers resides in the fact that when a failure occurs it is necessary to shut down the entire heat exchanger and repairs are extremely difficult to carry out.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a radial-flow heat exchanger which will achieve a substantially uniform through-flow ofthe fluid at the exterior of the tubes.

Another object of the present invention is to provide a radial-flow heat exchanger which can very readily be set up in such a way that compensations are easily made for manufacturing discrepancies, operating characteristics, and the like, so as to promote the desired uniformity in the through-flow of the exterior fluid.

Furthermore it is an object of the present invention to provide a construction of this type which makes it relatively simple to terminate the operation of only a part of the heat exchanger when and if this latter part should fail, so that the operations can continue with the remainder of the heat exchanger, with this remainder of the heat exchanger still functioning to provide the desired uniformity of through-flow of the exterior fluid.

Furthermore it is an object of the present invention to provide a radial flow heat exchanger construction which facilitates removing of a part of the heat exchanger, ifit fails, with rapid and convenient replacement of this part, without any major disturbance in the remainder of the heat exchanger, so that replacement of components can be very easily carried out with the heat exchanger of the invention.

However, basically it is an object of the invention to provide a construction which will achieve a uniform through-flow of the exterior fluid in the manner which will greatly increase the efficiency of the entire heat exchanger and which will compensate for any manufacturing errors or special considerations which are encountered during a given operation.

According to the invention the radial flow heat exchanger includes a tubular means which surrounds and is spaced from a given axis and which is composed of a plurality of tubes through which one of a pair of heat-exchanging fluids flows, The other of the pair of heat-exchanging fluids is adapted to flow radially across the tubes of the tubular means from an inner region thereof toward an outer region thereof, and in accordance with the invention the heat exchanger includes a fluid-guide means which directs this other fluid radially across the tubes of the tubular means in a manner which will achieve a uniformity of throughflow of the other fluid from the inner to the outer region of the tubular means.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this appli' cation and in which:

FIG. 1 is a schematic sectional elevation, in a plane which contains the axis of the heat exchanger, showing an arrangement according to one embodiment ofa heat exchanger of the invention;

FIG. 2 is an axial section of another embodiment ofa heat exchanger according to the invention where the heat exchanger is also schematically represented;

FIG. 3 is a schematic plan view of the heat exchanger of FIG. 2, although FIG. 3 also may be considered as a schematic plan view of the heat exchanger of FIG. I; and

FIG. 4 is a schematic fragmentary plan view of yet another arrangement of a heat exchanger according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings and first to FIG. 1, there is illustrated in FIG. 1 a heat exchanger where the exterior heat-exchanging fluid enters the heat exchanger at an inlet 12 and leaves the heat exchanger at an outlet 13. The heat exchanger includes a tubular means 3 composed of a plurality of tubes through which the second heat-exchanging fluid flows so that there will be an exchange of heat between the fluid at the interior of the tubes of the tubular means 3 and the fluid at the exterior thereof, this latter fluid enters at the inlet 12, flows radially across thetubes 3 at the exterior thereof and then discharges at the outlet 13. The tubular means 3 surrounds a predetermined central axis which extends vertically through the center of FIG.

I, and this tubular means 3 is composed of a plurality of tubes which in the illustrated example are curved to form tapered spirals which define uniform tubular paths defined by baffles, rings, or other spacers which are inserted between the tubes. The tubes which form the tubular means 3 are grouped so as to form a plurality of annular groups of tubes 4-8. The several groups 4-8 are situated respectively in annular chambers define between tapered baffles 9 of circular or annular configuration. Thus the several baffles 9, each of which forms part of a cone, defined between themselves chambers in which the several groups 4-8 are respectively accommodated and through which the exterior fluid flows radially as indicated by the arrows in FIG. 1.

A fluid-guide means coacts with the tubular means 3, which includes the baffles 9, to promote a uniform through-flow of the exterior gas radially across the exterior of the tubes of the tubular means 3 from the inlet 12 to the outlet 13. This fluid-guide means coacts with an inner region of the tubular means 3 for forming a receiving chamber which receives the fluid entering through the inlet 12 and with an outer region of the tubular means 3 for forming a discharge chamber which terminates in the outlet 13. The fluid-guide means is formed by a tapered tubular walls I, made of sheet metal, and it will be seen that this fluid-guide means includes a pair of these tubular, metal walls 1 which are tapered in the same direction. Thus, the inner tubular wall 1 of the fluid-guide means defines with the inner region of the tubular means 3 a receiving chamber I4 for receiving the exterior fluid, this receiving chamber 14 having the inlet 12 where the receiving chamber has its maximum cross section. Because of the taper of the wall I the receiving chamber 14 gradually diminishes in cross-section from the inlet 12 toward the opposed end of the tubular means 3. This receiving chamber I4 surrounds the central axis of the heat exchanger and the inner tubular wall 1 surrounds an inner space of the heat exchanger where, for example, a reactor may be accommodated. The outer tubular wall 1 of the fluidguide means defines with the outer region of the tubular means 3 a discharge chamber 15 which receives the exterior fluid after it has traveled radially across the tubes of the tubular means through the several chambers 4-8, and it will be noted that the cross section of the discharge chamber 15 gradually increases in the direction of flow of the exterior fluid toward the outlet 13.

The fluid-guide means of the invention includes, in addition to the tubular walls I a pair of perforated cylindrical walls 2 which are directly located next to the inner and outer regions of the tubular means 3. It is not essential to provide a fluid-guide means which includes walls I and 2 both at the entrance into and outlet from the tubular means. It is sufficient in many cases if a tubular cylindrical wall 2 of sheet metal or the like is provided only at the inner region of the tubular means 3.

The embodiment of the invention which is illustrated in FIG. 2 forms a radial-flow heat exchanger which is similar to that of FIG. 1, differing therefrom primarily in the fact that the tubes of the tubular means 3 form flat rather than tapered spirals. These flat spirals can be replaced, however, by circular tube sections which communicate one with the next and which surround each other. The reference characters applied to FIG. 1 apply in the same way to the embodiment of FIG. 2. the heat exchanger includes a supply header l0 communicating through a connecting tubular means 11 with the interiors of the tubes 3 for directing thereto the fluid which flows along the interior of the tubes 3, and this connecting tubular means ll extends from the tubular means 3 to a discharge header I7 which receives the interior fluid after it has passed through the tubular means3. Although the arrangement illustrated in FIG. 2 is one where the discharge header I7 is situated at the interior of the heat exchanger and the supply header 10 is at the exterior thereof, the arrangement can be reversed with the supply header being located adjacent the axis of the heat exchanger and the discharge header situated at the exterior of the tubular means. It is to be noted that it is only the tubular connecting means 11 which passes through the fluid-guide means formed by the tubular walls I and the perforated tubular walls 2. The supply header 10 is situated in an annular space defined between the outer wall I and an outer cylindrical wall of the heat exchanger, and of course in the reverse arrangement it would be the discharge header 17 which is located in this annular space. In this latter event the supply header 10 would be located in the central interior space 16 surrounded by the inner wall 1. The connecting tubular means 11 provides communication between the headers and the individual tubes in the groups 4,7, and 8. This is the specific arrangement which is illustrated in FIG. 2. It is important to provide an arrangement where all tubes of the tubular means which are supplied from one header l0 discharge their fluid to one or more headers 17 to form in this way a group which has no possibility ofa short-circuiting connection so that there can be no short-circuiting between groups of tubes. In the event of damage it thus becomes possible to stop the operation of only that group which has the damage, simply by closing the headers 10 and 17 of the damaged group of tubes. In order to avoid a greater lack of uniformity in the case of damage, an arrangement as shown in FIG. 2 is provided so that only individual tubes or groups 4-8 are served by given supply and discharge headers l0, 17. FIG. 3 schematically represents a plan of the arrangement of FIG. 2, or that of FIG. 1. At the central region 16 of the heat exchanger is possible to situate the core of a gas-cooled reactor. In this way it becomes possible for the radial heat-exchanger to form a compact and economical steam-generating unit. FIG. 3 schematically represents how a pair of tubular spirals of the tubular means 3 are supplied with fluid from a pair of the headers 10 and in turn have their fluid delivered to a pair of discharge headers 17, respectively. Thus, the several supply headers 10 are arranged vertically in the annular space between the discharge chamber 15 and the outer cylindrical wall of the heat exchanger while the several discharge headers 17 are arranged vertically in the interior space 16 in the manner shown in FIG. 3. Of course, the heat exchanger will include considerably more tubular spirals which are arranged parallel to each other in the same plane and there are additional tubular spirals distributed in parallel planes. One of the several tube-groups 4-8 is served by only one supply header l0 and one discharge header 17. The other headers illustrated in FIG. 3 serve to supply and discharge fluid to and from the tubes situated above and below those illustrated in FIG. 3.

FIG. 4 illustrates another embodiment of a radialflow heat exchanger of the invention, schematically in a plan view. In this case the several groups 48 of the tubes of the tubular means 3 are arranged in sectorshaped arcuate chambers which together form a complete circle around the central axis of the heat exchanger. In each of these sector-shaped chambers there is a sector-shaped group of tubes where each tube has a sinuous configuration extending back and forth in the arcuate chamber in the manner illustrated in FIG. 4. With this embodiment the supply headers I0 as well as the discharge headers 17 are situated directly within the areuate, sector-shaped chambers for the several groups of tubes. The use of a connecting tubular means ll thus becomes unnecessary with this embodiment. Thus, as is clearly illustrated in FIG. 2, it is necessary with the latter embodiment for the connecting tubular means 11 to pass through the tubular walls 1, and of course this requirement is completely eliminated with the embodiment of FIG. 4. Thus the construction as shown in FIG. 4 provides a heat exchanger which is simpler and more reliable in operation than that of FIG. 2.

The receiving chamber 14 and discharge chamber defined between the tubular walls I and the perforated walls 2 are dimensioned in such a way that the entrance and discharge cross sections maintain with respect to each other a relationship in accordance with the square root of the temperature of the fluid flowing into and out of the supply and discharge chambers, so that at any given cross section of one of the chambers 14 and 15 there will be a cross-sectional area in accordance with this relationship. As a result of this dimensioning a uniform speed of flow into the receiving chamber 14 and out of the discharge chamber 15 is achieved, so that flow losses are reduced to a minimum.

Furthermore, the openings of the perforated walls 2 are provided with sizes and distributions which will result in flowing of equal amounts of exterior fluid through the several groups of 4-8 of the tubular means 3. Thus, the sizes and distributions of the openings of the inner wall 2 are such that the resistance to flow of the exterior fluid gradually dimenishes in the direction from the inlet 12 toward the opposite end of the tubular means 3, so that where the cross section of the receiving chamber 14 is the smallest there is at the same time the least resistance to flow while at the inlet 12 where the cross section is at a maximum there is the greatest resistance to flow of the exterior fluid. At the discharge chamber IS the reverse arrangement is provided in that the sizes and distribution of the openings of the-outer perforated wall 2 are such that from the smallest cross section of chamber 15 toward the largest cross section thereof, where the outlet 13 is situated, the resistance to flow of the exterior fluid through the outer wall 2 gradually increases, thus achieving in this case also the greatest resistance to flow at the area of greatest cross section of the discharge chamber. In this way the perforated walls 2 contribute toward the maintaining of a uniform through-flow of the exterior fluid.

Furthermore, it is possible to provide a construction where the perforations of the walls 2 can be changed, so that after the first operation of the heat exchanger, non-uniformity in the through-flow at the individual groups of tubes can be compensated. Such nonuniformity can result from lack of uniform heating of the individual tubes so that under certain circumstances individual length of tubes will have localized over-heating. Also, lack of uniformity in the heat transfer can be compensated in a similar manner if, for example, after repair of the heat exchanger individual tube lengths are closed.

Thus, for these purposes the tubular perforated walls 2 are constructed in such a way that by welding of covering plates thereon or by placing ring-shaped covering sheets around selected areas of one or the other of the tubular walls 2, the distribution of the perforations can be changed to achieve the desired uniformity in the through-flow of the exterior fluid. For the purposes of stability the perforated walls 2 are situated as close as possible to the inner and outer regions of the tubular means 3. As was indicated above, the situation of a tubular wall 2 at the discharge chamber 15 is in general less effective, but at the same time is for the most part of advantage because by utilizing such a structure it is possible to avoid the necessity of material having a high heat resistance. In other words, because of the increase in the uniformity of flow resulting from these constructions localized overheated regions can be avoided and thus the requirement of expensive heatresistant material can be eliminated or reduced.

In order to increase the convenience and possibility of repairing the heat exchanger, the headers 10 and 17 preferably take the form of straight pipes. In this way plugging devices can be introduced through such pipes to plug the ends of selected lengths of the tubes of the tubular means 3 when such a length becomes defective or damaged for any reason. If because of the requirements of a particular construction it is not possible to provide headers 10 and 17 which are straight, then an arrangement as shown in FIG. 2 is provided since with this arrangement it is possible to introduce individual tubular spirals or even individual groups of tubes into different planes.

The particular embodiment of the heat exchanger which is illustrated in FIG. 4 has a special advantage in connection with repair, because with this construction in individual sector-shaped section can have its operation terminated and, if desired, an entire sector-shaped section of the heat exchanger can simply be replaced in a simple manner. In connection with the sizes and distributions of the openings of the perforated walls 2, these sizes and distributions will be such that at the inner wall 2 from the inlet 12 toward opposed end of the tubular means 3 there will be a gradually increasing number ofopenings in the wall 2 per unit of area and/or the sizes of the openings will gradually increase, thus reducing the resistance to flow in this direction from the bottom toward the top of FIG. 1, while the reverse arrangement will be provided at the outer wall 2 in that the number of openings of the wall 2 will gradually diminish from the bottom toward the top of FIG. 1 and/or the sizes of these openings will become gradually smaller in the same direction so that the resistance to flow will gradually increase in this upper direction at the outer perforated wall 2 of FIG. 1.

It is thus apparent that with the structure described above and shown in the drawings the radial-flow heat exchanger of the invention will achieve a uniformity in the through'flow of the exterior fluid, in a manner enabling compensation to be made for manufacturing inaccuracies as well as for particular operating conditions, such as when and if repairs are required with consequent elimination of part of the tubes from the operation.

What is claimed is:

1. In a radial-flow heat exchanger, tubular means surrounding a given axis and composed of a plurality of tubes'which are curved around said axis and through which one ofa pair of heat-exchanging fluids is adapted to flow, said tubular means having an inner region directed toward said axis and an outer region directed away from said axis and the other of said pair of heatexchanging fluids being adapted to flow at the exterior of the tubes of said tubular means from said inner region to said outer region thereof, and fluid-guide means coacting with at least one of said regions of said tubular means for controlling the flow of said other fluid at said inner and outer regions of said tubular means and for maintaining a substantially uniform through-flow of said other fluid radially with respect to said axis from said inner to said outer region of said tubular means in all axial sections of said tubular means.

2. The combination of claim 1 and wherein said fluid-guide means includes an inner tubular wall coaxial with said tubular means and coacting with said inner region thereof for controlling the flow of said other fluid to said inner region of said tubular means and an outer tubular wall coaxial with said tubular means and coacting with said outer region of said tubular means for controlling the flow of said other fluid at said outer region of said tubular means.

3. The combination of claim 2 and wherein said tubular walls are tapered and respectively form parts of cones.

4. The combination of claim 1 and wherein said fluid-guide means includes at least at said inner region of said tubular means a cylindrical perforated wall coaxially surrounding said axis and formed with a plurality of openings through which said other fluid must flow before reaching said inner region of said tubular means.

5. The combination of claim 4 and wherein a second perforated tubular wall forms part of said fluid-guide means and surrounds said tubular means at said outer region thereof.

6. The combination of claim 1 and wherein said tubular means is composed of a plurality of groups of tubes and includes baffles defining chambers for respectively accommodating said groups of tubes and for compelling said other fluid to flow radially through said chambers from said inner to said outer region of said tubular means in engagement with the several groups of tubes in said chambers.

7. The combination of claim 1 and wherein said fluid-guide means includes an inner tubular wall located adjacent and surrounded by said inner region of said tubular means and an outer tubular wall located adjacent and surrounding said outer region of said tubular means, said tubular walls of said fluid-guide means being coaxial with said tubular means and both of said tubular walls tapering in the same direction along their common axis, said inner tubular wall defining with one end of said tubular means an inlet for said other fluid to said inner region of said tubular means and said outer tubular wall defining with an opposed end of said tubular means an outlet for said other fluid at said other end of said tubular means, said inner wall having its minimum diameter at said inlet and said outer wall having its maximum diameter at said outlet with said inner wall defining with said inner region of said tubular means a receiving chamber for said other fluid which gradually diminishes in cross section from said inlet toward said outlet while said outer wall of said tubular means defines with said outer region of said tubular means a discharge chamber for said other fluid which gradually increases in cross section from said inlet toward said outlet.

8. The combination of claim 7 and wherein the maximum cross section of the space defined between said walls of said fluid-guide means and said inner and outer regions of said tubular means varies according to the square root of the temperature of said other fluid.

9. The combination of claim 1 and wherein said fluid-guide means defines an inner space which contains said axis and is surrounded by an outer space, a pair of headers respectively located in the latter spaces for supplying said one fluid to and from the interior of the tubes of said tubular means, and connecting tubular means connected to and communicating with said pair of headers, on the one hand, and connected to and communicating with the tubes of said tubular means, on the other hand, for directing the flow of said one fluid between said headers and the tubes of said tubular means, said connecting tubular means extending through said fluid-guide means.

10. The combination of claim 9 and wherein said headers are each in the form of straight pipes.

11. The combination of claim 1 and wherein said fluid-guide means includes an inner tapered tubular wall coaxial with said tubular means and surrounded by said inner region thereof for defining a receiving chamber for said other fluid with said receiving chamber having an inlet at that end of said tubular wall which is of minimum diameter so that the receiving chamber gradually diminishes in cross section from said inlet of said receiving chamber toward an end thereof opposed to said inlet, and said fluid-guide means including a tubular perforated wall surrounding said tapered wall and situated closer to said inner region of said tubular means, said perforated tubular wall having in the direction of flow of said other fluid from said inlet of said receiving chamber toward said opposed end thereof openings the distribution and size of which provide for said other fluid at said inner region of said tubular means a resistance to flow which gradually diminishes from said inlet of said receiving chamber toward said opposed end thereof, so that while said receiving chamber gradually diminishes in cross section the resistance to flow of said other fluid to said inner region of said tubular means also gradually diminishes for I promoting the uniformity of through-flow of said other fluid.

12. The combination of claim 11 and wherein said fluid-guide means includes an outer tubular wall surrounding said outer region of said tubular means and being tapered in the same direction as said inner tubular wall, and an outer perforated wall surrounded by said outer tubular wall and formed with perforations at said outer region of said tubular means, and said outer perforated wall having a size and distribution of openings which provide a gradually increasing resistance to the flow of said outer fluid at said outer region of said tubular means in the same direction that the resistance to flow of said other fluid decreases at said inner perforated tubular wall, said outer tubular wall defining with said outer region of said tubular means a discharge chamber which gradually increases in cross section in the same direction that the resistance to flow provided by said outer perforated wall increases for also contributing to the uniformity of through-flow.

13. The combination of claim 11 and wherein said perforated tubular wall is provided with a means for regulating the resistance to flow of said other fluid therethrough for compensating for irregularities in the through-flow.

14. The combination of claim 1 and wherein the tubes of said tubular means form parts of a plurality of groups of tubes, a plurality of supply headers communicating with said groups of tubes for supplying said one fluid thereto and a plurality of discharge headers also communicating with said groups of tubes for receiving said one fluid therefrom, said supply headers communicating through said groups of tubes only with predetermined discharge headers, respectively, so that for every one supply header there is one discharge header receiving fluid from said one supply header after the latter fluid has passed through at least one of said groups of said tubular means, so that if necessary it is possible to interrupt the flow of said one fluid at a selected supply header while maintaining the flow of said one fluid at the other supply and discharge headers and the groups of tubes communicating therewith.

15. The combination of claim 1 and wherein said tubes of said tubular means are in the form of ringshaped groups each of which forms a tubular assembly of tapered configuration.

16. The combination of claim 1 and wherein said tubes of said tubular means are in the form of ringshaped groups of tubes with each group surrounding said axis, and defining a tubular assembly which has opposed ends in planes normal to said axis and parallel to each other.

17. The combination of claim 1 and wherein said tubular means includes baffles respectively situated in planes which contain said axis and which form arcuate chambers, said tubes of said tubular means being divided into groups respectively located in said chambers with the group of tubes in each chamber progressing sinuously back and forth between a pair of successive baffles and between the inner and outer region of said tubular means. 

1. In a radial-flow heat exchanger, tubular means surrounding a given axis and composed of a plurality of tubes which are curved around said axis and through which one of a pair of heatexchanging fluids is adapted to flow, said tubular means having an inner region directed toward said axis and an outer region directed away from said axis and the other of said pair of heatexchanging fluids being adapted to flow at the exterior of the tubes of said tubular means from said inner region to said outer region thereof, and fluid-guide means coacting with at least one of said regions of said tubular means for controlling the flow of said other fluid at said inner and outer regions of said tubular means and for maintaining a substantially uniform through-flow of said other fluid radially with respect to said axis from said inner to said outer region of said tubular means in all axial sections of said tubular means.
 2. The combination of claim 1 and wherein said fluid-guide means includes an inner tubular wall coaxial with said tubular means and coacting with said inner region thereof for controlling the flow of said other fluid to said inner region of said tubular means and an outer tubular wall coaxial with said tubular means and coacting with said outer region of said tubular means for controlling the flow of said other fluid at said outer region of said tubular means.
 3. The combination of claim 2 and wherein said tubular walls are tapered and respectively form parts of cones.
 4. The combination of claim 1 and wherein said fluid-guide means includes at least at said inner region of said tubular means a cylindrical perforated wall coaxially surrounding said axis and formed with a plurality of openings through which said other fluid must flow before reaching said inner region of said tubular means.
 5. The combination of claim 4 and wherein a second perforated tubular wall forms part of said fluid-guide means and surrounds said tubular means at said outer region thereof.
 6. The combination of claim 1 and wherein said tubular means is composed of a plurality of groups of tubes and includes baffles defining chambers for respectively accommodating said groups of tubes and for compelling said other fluid to flow radially through said chambers from said inner to said outer region of said tubular means in engagement with the several groups of tubes in said chambers.
 7. The combination of claim 1 and wherein said fluid-guide means includes an inner tubular wall located adjacent And surrounded by said inner region of said tubular means and an outer tubular wall located adjacent and surrounding said outer region of said tubular means, said tubular walls of said fluid-guide means being coaxial with said tubular means and both of said tubular walls tapering in the same direction along their common axis, said inner tubular wall defining with one end of said tubular means an inlet for said other fluid to said inner region of said tubular means and said outer tubular wall defining with an opposed end of said tubular means an outlet for said other fluid at said other end of said tubular means, said inner wall having its minimum diameter at said inlet and said outer wall having its maximum diameter at said outlet with said inner wall defining with said inner region of said tubular means a receiving chamber for said other fluid which gradually diminishes in cross section from said inlet toward said outlet while said outer wall of said tubular means defines with said outer region of said tubular means a discharge chamber for said other fluid which gradually increases in cross section from said inlet toward said outlet.
 8. The combination of claim 7 and wherein the maximum cross section of the space defined between said walls of said fluid-guide means and said inner and outer regions of said tubular means varies according to the square root of the temperature of said other fluid.
 9. The combination of claim 1 and wherein said fluid-guide means defines an inner space which contains said axis and is surrounded by an outer space, a pair of headers respectively located in the latter spaces for supplying said one fluid to and from the interior of the tubes of said tubular means, and connecting tubular means connected to and communicating with said pair of headers, on the one hand, and connected to and communicating with the tubes of said tubular means, on the other hand, for directing the flow of said one fluid between said headers and the tubes of said tubular means, said connecting tubular means extending through said fluid-guide means.
 10. The combination of claim 9 and wherein said headers are each in the form of straight pipes.
 11. The combination of claim 1 and wherein said fluid-guide means includes an inner tapered tubular wall coaxial with said tubular means and surrounded by said inner region thereof for defining a receiving chamber for said other fluid with said receiving chamber having an inlet at that end of said tubular wall which is of minimum diameter so that the receiving chamber gradually diminishes in cross section from said inlet of said receiving chamber toward an end thereof opposed to said inlet, and said fluid-guide means including a tubular perforated wall surrounding said tapered wall and situated closer to said inner region of said tubular means, said perforated tubular wall having in the direction of flow of said other fluid from said inlet of said receiving chamber toward said opposed end thereof openings the distribution and size of which provide for said other fluid at said inner region of said tubular means a resistance to flow which gradually diminishes from said inlet of said receiving chamber toward said opposed end thereof, so that while said receiving chamber gradually diminishes in cross section the resistance to flow of said other fluid to said inner region of said tubular means also gradually diminishes for promoting the uniformity of through-flow of said other fluid.
 12. The combination of claim 11 and wherein said fluid-guide means includes an outer tubular wall surrounding said outer region of said tubular means and being tapered in the same direction as said inner tubular wall, and an outer perforated wall surrounded by said outer tubular wall and formed with perforations at said outer region of said tubular means, and said outer perforated wall having a size and distribution of openings which provide a gradually increasing resistance to the flow of said outer fluid at said outer region of said tubular meanS in the same direction that the resistance to flow of said other fluid decreases at said inner perforated tubular wall, said outer tubular wall defining with said outer region of said tubular means a discharge chamber which gradually increases in cross section in the same direction that the resistance to flow provided by said outer perforated wall increases for also contributing to the uniformity of through-flow.
 13. The combination of claim 11 and wherein said perforated tubular wall is provided with a means for regulating the resistance to flow of said other fluid therethrough for compensating for irregularities in the through-flow.
 14. The combination of claim 1 and wherein the tubes of said tubular means form parts of a plurality of groups of tubes, a plurality of supply headers communicating with said groups of tubes for supplying said one fluid thereto and a plurality of discharge headers also communicating with said groups of tubes for receiving said one fluid therefrom, said supply headers communicating through said groups of tubes only with predetermined discharge headers, respectively, so that for every one supply header there is one discharge header receiving fluid from said one supply header after the latter fluid has passed through at least one of said groups of said tubular means, so that if necessary it is possible to interrupt the flow of said one fluid at a selected supply header while maintaining the flow of said one fluid at the other supply and discharge headers and the groups of tubes communicating therewith.
 15. The combination of claim 1 and wherein said tubes of said tubular means are in the form of ring-shaped groups each of which forms a tubular assembly of tapered configuration.
 16. The combination of claim 1 and wherein said tubes of said tubular means are in the form of ring-shaped groups of tubes with each group surrounding said axis, and defining a tubular assembly which has opposed ends in planes normal to said axis and parallel to each other.
 17. The combination of claim 1 and wherein said tubular means includes baffles respectively situated in planes which contain said axis and which form arcuate chambers, said tubes of said tubular means being divided into groups respectively located in said chambers with the group of tubes in each chamber progressing sinuously back and forth between a pair of successive baffles and between the inner and outer region of said tubular means. 